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The work is devoted to the study of the structure of the elastic stress field in the area of junctions of grain boundaries containing strain-induced rotational-shear mesodefects. The jumps in plastic distortion of grains when passing through grain boundaries create additional misorientations on them, the mismatch of which at the junctions of grains leads to the appearance of linear mesodefects of the rotational type – junction disclinations. Planar mesodefects of the shear type appear on the flat sections of the boundaries, which are plastic shears uniformly distributed along the boundaries. These mesodefects create spatially inhomogeneous elastic stress fields near the junctions and ledges of the grains. They increase during plastic deformation and, at sufficiently large value of strain, initiate the formation of a fragmented material structure. Rotational-shear mesodefects are also the cause of the nucleation and accumulation of microcracks at the stage of viscous fracture of polycrystalline solids. In this work, asymptotic formulas are obtained that make it possible to analyze the distribution and anisotropy of the internal stress field in the vicinity of the grain junction from rotational-shear mesodefects. It was found that the components of the stress field weakly depend (logarithmically) on the length of the grain boundaries formatting junction of the grains. It is shown that the screening disclination of the dipole leads to the appearance of an angular dependence of the diagonal components of the elastic stress tensor in the vicinity of the junctions and its contribution to the elastic field of the disclinations dipole is about 10–15%. The obtained asymptotic expressions can be used to study the kinetics of a dislocation ensemble and to analyze the conditions for the nucleation of microcracks in the vicinity of joints and ledges of grains.

Oriented “shish-kebab” structures could be obtained by shearing to enhance the mechanical properties of polymer samples markedly. However, the effect of shear mode on mechanical properties is still uncertain. The study of stepped hoop shear field on the isotactic polypropylene (iPP) pipe was developed through applying a self-designed rotational shear system (RSS). The effect of stepped shear field on the microstructure and comprehensive properties of iPP pipe was investigated by the comparison with continuous shear. It could be found that the loosely-assembled shish-kebabs with the larger size were formed in the continuous shear pipes, but the smaller and tightly-stacked ones existed in the pipes with stepped shear. Surprisingly, due to differential morphologies under different shear modes, better comprehensive mechanical properties were obtained in the pipes with stepped shear.

To increase the maximum internal pressure that a polyethylene (PE) pipe can withstand, a novel rotational shear system (RSS) was constructed in this study to fabricate PE pipes with enhanced hoop strength by applying hoop shear on the pipes using a rotational mandrel. The microstructure and morphology with the influences of melt plasticizing temperature on PE pipes processing under rotational shear were investigated indirectly using small-angle X-ray scattering and wide-angle X-ray diffraction (SAXS/WAXD) measurements. In the SAXS patterns, equatorial streaks and meridional scattering peaks were clearly observed in all three samples prepared at different melt plasticizing temperatures, 215, 235, and 255 °C. Their presence indicated that shish-kebab crystals form in rotational shear. Compared to those at the low melt temperature, the increase in the melt temperature enhanced the amount and the dimensions of shish formed. However, the shish also relaxed faster at the high melt temperature. This behavior was attributed to the enhancement of the molecular chain's athletic ability. The hoop tensile strength and the heat resistance of the pipes peaked at the melt plasticizing temperature of 235 °C, 75.2 MPa, 102.4 °C, up 1 MPa, 0.2 °C (compared to the 215 °C) and 7.8 MPa, 3.2 °C (compared to the 255 °C). The axial strength increased with an increase of melt plasticizing temperature. However, the increase of melt plasticizing temperature worsens the inherent good tensile toughness of PE100 pipes as the axial elongation at break decreases.

In this paper, the experimental activity was carried out on five pulverized coals with different particle sizes taken from the industrial demonstration plant of SE-Gasifier Pulverized Coal Gasification in Nanjing, China. Flow properties of pulverized coal including powder cohesion, angle of internal friction and tensile strength were determined by the rotational shear cell accessory of Freeman FT4 Powder Rheometer. These pulverized coal samples were further discharged from a bench-scale discharge system and an industrial device in the SE gasification industrial plant. The effects of mean particle size, fine contents and hopper pressure on the flow properties and the discharge of pulverized coal were discussed. The tensile strength was used to correlate with the feeding characteristics of pulverized coal and proved to be an effective indicator to describe the powder feeding performance. A combination of a continuum approach and a particle–particle approach was therefore built to predict the tensile strength. The model, considered the elastic deformation, was further modified by taking into account the effect of particle size distribution. The predicted tensile strengths were compared with those obtained from the Mohr-Coulomb approach, giving errors mostly below ±25%. It was therefore considered as a valuable way to provide reference for the evaluation of feeding characteristics of pulverized coal for entrained-flow gasification.

With the growth in underwater construction activities, there is an increasing need for accurate seabed engineering data. Modern technology makes it possible to take samples of bottom soils with a partially disturbed structure, especially for weak silty soils and silts. Testing such samples in laboratory conditions leads to inevitable errors. Despite the constant improvement of technical means of sampling, they cannot fully replace studies of the properties of bottom soils in natural occurrence. Therefore, it became necessary to create devices for the natural study of underwater soils. The following soil investigation methods are used in deep-sea wells: stamp tests, rotational shear, penetration logging, soil cutting, pressuremetry. Drilling of underwater wells at the bottom is carried out from floating drilling rigs, consisting of a floating base and a drilling rig. Pontoons (catamarans, trimarans) and drilling ships (self-propelled and non-self-propelled) are used as a base. On the shelf, pontoons with retractable supports or a flooded base are more often used. The drilling rig with working equipment is usually placed in the center of the pontoon. The choice of drilling equipment is determined by the purpose of the work, the depth and diameter of underwater wells, the depth of the sea, the displacement of the drilling rig, the physical and mechanical properties of bottom, soil, etc. Deep-sea drilling is carried out from special vessels on which the drilling unit is mounted. Vessels with an opening bottom or a special shaft for the passage of casing and drill pipes, as well as those with retractable cantilever platforms, are used. Drilling ships and pontoons are kept in a fixed position with the help of four or six anchors attached to the bow and stern of the craft. Drilling rigs provide rotary, percussion-rotary, shock-rope, vibration, rotary suction and airlift drilling. Drilling at maximum depths in the ocean is carried out using deep-sea bottom platforms and autonomous controlled vehicles., С ростом подводного строительства возрастает потребность в точных инженерных данных морского дна. Современная техника позволяет брать пробы донных грунтов с частично нарушенной структурой, особенно слабых грунтов и илов. Испытания таких образцов в лабораторных условиях приводит к неизбежным погрешностям. Несмотря на постоянное совершенствование технических средств пробоотбора, они не могут полностью заменить исследования свойств донных грунтов в естественных условиях. Поэтому возникла необходимость в создании устройств для натурного изучения подводных грунтов. В глубоководных скважинах применяются следующие методы исследования грунта: штамповые испытания, вращательный срез, пенетрационный каротаж, резание грунтов, прессиометрия. Бурение подводных скважин на дне осуществляется с плавбазы и буровой установки. В качестве базы используют понтоны (катамараны, тримараны) и буровые суда (самоходные и несамоходные). На шельфе чаще применяют понтоны с выдвижными опорами или затопленным основанием. Буровую вышку с рабочим оборудованием обычно размещают в центре понтона. Выбор бурового определяется обусловлен целью работ, глубиной и диаметром подводных скважин, глубиной моря, водоизмещением буровой установки, физико-механическими свойствами донного грунта и др. Глубоководное бурение проводят со специальных судов, на которых смонтирована буровая установка. Применяются суда с открывающимся днищем или специальной шахтой для пропуска обсадных и бурильных труб, а также с выдвижными консольными платформами. Буровые суда и понтоны удерживают в неподвижном положении с помощью четырех или шести якорей, закрепленных на носу и корме плавсредства. Буровые установки обеспечивают вращательное, ударно-вращательное, ударно-канатное, вибрационное, вращательно-всасывающее и эрлифтное бурение. Бурение на максимальных глубинах в океане осуществляется с помощью глубоководных донных платформ и автономных управляемых аппаратов., Зі зростанням підводного будівництва зростає потреба в точних інженерних даних морського дна. Сучасна техніка дозволяє брати проби донних ґрунтів із частково порушеною структурою, особливо слабких ґрунтів та мулів. Випробування таких зразків у лабораторних умовах призводить до неминучих похибок. Незважаючи на постійне вдосконалення технічних засобів пробовідбору, вони не можуть повністю замінити дослідження властивостей донних ґрунтів у природних умовах. Тому виникла потреба у створенні пристроїв для натурного вивчення підводних грунтів. У глибоководних свердловинах застосовуються такі методи дослідження ґрунту: штампові випробування, обертальний зріз, пенетраційний каротаж, різання ґрунтів, пресіометрія. Буріння підводних свердловин на дні здійснюється з плавбази та бурової установки. Як базу використовують понтони (катамарани, трімарани) і бурові судна (самохідні та несамохідні). На шельфі частіше застосовують понтони з висувними опорами або затопленою основою. Бурову вежу з робочим обладнанням зазвичай розміщують у центрі понтона. Вибір бурового визначається зумовлено метою робіт, глибиною та діаметром підводних свердловин, глибиною моря, водотоннажністю бурової установки, фізико-механічними властивостями донного ґрунту та ін. Глибоководне буріння проводять із спеціальних суден, на яких змонтовано бурову установку. Застосовуються судна з днищем, що відкривається, або спеціальною шахтою для пропуску обсадних і бурильних труб, а також з висувними консольними платформами. Бурові судна та понтони утримують у нерухомому положенні за допомогою чотирьох або шести якорів, закріплених на носі та кормі плавзасобу. Бурові установки забезпечують обертальне, ударно-обертальне, ударно-канатне, вібраційне, обертально-всмоктувальне та ерліфтне буріння. Буріння на максимальних глибинах в океані здійснюється за допомогою глибоководних донних платформ та автономних керованих апаратів.

This study develops a damage mechanics-based crack growth model to predict crack length in a typical viscoelastic material (i.e. bitumen) under a rotational shear fatigue load. This crack growth model was derived using torque and dissipated strain energy equilibrium principles. The crack length was predicted using bitumen?s shear moduli and phase angles in the undamaged and damaged conditions, measured by linear amplitude sweep (LAS) tests and time sweep (TS) tests, respectively. The two tests were both performed using Dynamic Shear Rheometer (DSR), thus the crack growth model was named as a DSR-C model. To validate the DSR-C model, the crack lengths after the TS tests were measured using digital visualisation of cracking surfaces for one virgin bitumen and one polymer-modified bitumen at two temperatures (15, 20°C), two frequencies (10, 20Hz) and two strain levels (5%, 7%) under unaged and aged conditions. Results show that the DSR-C model can accurately predict the crack length in the viscoelastic bitumen under the rotational shear fatigue load at different loading and material conditions. The crack growth includes initial transition period, steady growth period and rapid growth period under a controlled strain loading mode. The degradation of the material property results from the crack growth that initiates from the outer edge toward the centre of the sample under the rotational shear load.

This paper is devoted to the study of the stability dynamics of wave processes of flat and circularelements, and also some axisymmetric problems of oscillation of an elastic layer limited by rigid or deformableboundaries when exposed to normal or rotational shear stresses are considered. Solutions to the problems underconsideration were obtained using integral transformations by coordinate or time. The work develops the dynamicstability of a round rod. The loss of stability of a round rod will be investigated on the basis of the mathematicaltheory and the transverse oscillations of a round rod, described in the work of I.G. Philippov.

How expressively and freely a horse moves depends on many factors. Two important factors are the slip resistance and riding safety of the surface on which it is moving. Numerous studies have already been carried out not only on how a horse places its feet on different types of surfaces but also on the cohesiveness of the footing surface with respect to the shear forces that are in action. Little is known at present, however, about the rotational shear resistance (RSR) of a footing, which is engendered by a horse hoof turning on its surface. In a technical investigation, the RSR (measured as the maximum moment of torque [TMax] which was necessary to turn a traction tester [TT] through 45°) of two different types of riding arena surface (sand [S] and sand fiber [SF]) were investigated according to their moisture content and the operator (operator A or operator B) using the TT. A subsequent 4-week field study was used to investigate the effects of the factors sampling location, moisture content, number of days after the last arena grooming session, and the type of horseshoe stud on the RSR values (TMax) of an indoor riding arena surface. The RSR measurements were carried out daily for 4 weeks using the TT. The moisture content of the footing was determined before each of the RSR measurements in both the technical and field investigations. In the technical investigation, it could be shown that both the TT operator and the moisture content significantly influenced the TMax values, but not the footing composition. Despite standardized experimental conditions, operator B measured 12.73% higher TMax values than operator A when using the TT. There was a linear relationship between the moisture content and TMax values of both types of footing: the RSR of both the S and SF surfaces increased with increasing moisture content. There was, however, no significant difference in the RSR between the two types of footing. In the field investigation, the sampling location in the indoor riding arena, the number of days after the last arena grooming session, the use of studs, and the moisture content all had a significant influence on the TMax values. Significant differences in TMax occurred depending on the sampling location in the indoor riding arena. Arena grooming led to a significant reduction in the RSR of the footing, although only on the day when the grooming took place. The use of studs led to 27.47%–65.18% higher TMax values than when no studs were used. Important for the increase in TMax values was the stud length as higher TMax values could be measured with increasing length. Furthermore, a linear relationship between the moisture content and the TMax values could be observed in the experiments without studs.

This study aims to characterise the healing properties of asphalt binders at different damage levels. The healing and the damage levels were quantified by crack length (CL) in binder samples generated by rotational shear fatigue loads in strain-controlled dynamic shear rheometer (DSR) tests. For comparison, the healing was also characterised by the commonly used material parameters including pseudo shear stiffness (S) and dissipated pseudo strain energy (DPSE). A normalized healing index was formulated using the above three parameters, respectively. A healing test of polymer-modified bitumen was designed based on DSR including a strain-controlled time sweep test plus a rest duration and followed by another strain-controlled time sweep test. The healing tests were performed at different rest start times (5min, 10min and 20min), rest durations (5s, 10s, 0.5min, 1min, 2min, 5min, 10min, 20min, and 40min), and amplitudes of the shear strain (5%, 7%, and 10%) at 20 °C and 10 Hz. Results show that the CL-based healing index is a fundamental and accurate parameter to evaluate the healing rate and healing potential of the bitumen. DPSE-based healing index is applicable only when the energy is mainly dissipated to generate cracks. Healing is underestimated when characterised using S or DPSE-based healing indices. Healing index increases due to the advance of rest duration or the decrease of the damage level, and the healing rate can be essentially modelled by Ramberg-Osgood model. Higher damage levels (introduced by higher load levels or longer loading time) can effectively decrease the binders’ healing potentials when the binders are at the relatively low damaged levels. The healing potential becomes low when the material is at severe damage state, thus will remain at that low levels even though the damage level increases.

We previously proposed a bimodal incoherent digital holography system to implement both three-dimensional and infinite depth-of-field (DOF) imaging. In this paper, we reveal the basic operation of our system in detail to control its imaging properties such as transverse magnification and DOF. We numerically evaluated the effect of rotational shear on these imaging properties, and the results indicate that it is possible to control both properties by simply changing the rotation angle of a light instead of replacing an imaging lens.

Fatigue resistance of bituminous binders plays a critical role in determining the fatigue performance of asphalt pavements. It is reported in the literature that, under a rotational shear fatigue load like a dynamic shear rheometer (DSR) test, the crack grows in the cylindrical bitumen sample as a circumferential crack that is initiated at the periphery of the sample and propagates toward the center of the sample. This study aims to model this crack propagation in bituminous binders under rotational shear fatigue load by time sweep (TS) fatigue test using the DSR. The crack length in the TS test is determined using a damage mechanics-based DSR-C model which is a function of the shear moduli and phase angles under undamaged and damaged conditions. The crack evolution is modeled by a pseudo J-integral based Paris’ law. Samples of virgin bitumen 40/60 and polymer-modified bitumen X-70 under unaged and aged conditions are tested by the TS tests at different temperatures, frequencies, and strain levels. Results show that the pseudo J-integral Paris’ law is able to predict accurately the crack propagation in bituminous binders under the rotational shear fatigue load. The crack grows faster in aged bitumen or at lower temperatures. The Paris’ law model parameters ( A and n) are independent of loading frequency or load amplitude. They are fundamental material properties and can be determined at one loading frequency and amplitude, then can be implemented to predict the growth of cracks in bituminous binders at different loading frequencies or amplitudes.

Research on multi-hazard prevention and mitigation in building structures is the most recent developing trend in civil engineering. In this study, an analytical model is proposed to calculate the structural resistance of a type of multi-hazard resilient prefabricated concrete (MHRPC) frame under earthquake and column removal scenarios. The MHRPC frame is assembled using prefabricated RC beams and columns, unbonded post-tensioning (PT) tendons, energy-dissipating steel angles, and large rotational shear plates. According to the experimental results, the MHRPC frame exhibits the features of low damage and self-centering under seismic loading. Meanwhile, when subjected to column removal scenarios, the MHRPC frame is proven to demonstrate a high progressive collapse resistance. In order to calculate the seismic and progressive collapse resistance of the MHRPC frame, analytical models for the critical components in the MHRPC frame (PT tendons and steel angles) are compared and selected based on the experimental results and numerical simulations. Furthermore, calculation methods for the seismic and progressive collapse resistance of the MHRPC frame specimens are proposed. The calculation results are validated using the experimental results. This study could provide a reference for the design of MHRPC frame structures, considering both earthquake and progressive collapse.

This study aims to model fatigue crack initiation in bituminous binders. An energy-based crack initiation criterion is developed for bitumen under a rotational shear fatigue load. Based on a damage mechanics analysis of fatigue cracking process, the crack initiation is defined and local energy redistribution around crack tips due to ‘factory-roof’ cracking is quantified. A quantitative energy criterion is proposed for the fatigue crack initiation in the bitumen using viscoelastic Griffith’s theory. The crack initiation criterion is validated through comparing the predicted and measured surface energy of the bitumen. The results show that bitumen fatigue cracking under the rotational shear fatigue load can be divided into two stages: the edge flow damage and the ‘factory-roof’ cracking. The crack initiation is dependent of the shear modulus and surface energy of bituminous binders, critical crack size, and loading amplitude. The energy-based crack initiation criterion along with the DSR fatigue tests can be potentially used to determine the material surface energy.

Switchgrass is a perennial herbaceous plant regarded as a biomass energy crop in the United States for its high adaptability and yield potential. Processing and handling of switchgrass particles are challenging due to the erratic mechanical and flow behavior originating from their intrinsic particulate properties. In this work, we present a bonded-sphere discrete element model designed specifically for switchgrass particles. The model simultaneously captures three key particulate features, i.e., fibrous particle shapes, a wide range of particle sizes, and particle deformability. Realistic yet computationally efficient particle shape templates are created based on the image analysis data of switchgrass specimens. A fitting procedure is proposed to ensure both the particle width and length distributions are captured, a unique requirement for fibrous particles. Two full-scale numerical models, i.e., a uniaxial compression model and a Schulze ring shear model, are developed using information from physical experiments. The model is calibrated using experimental data of chopped-small switchgrass specimens, and then, is validated using data of chopped-large specimens in both compression and ring-shear tests. Numerical results show that the numerical models capture bulk densities accurately (with an error of 3%) while slightly underestimate the bulk friction angle. Furthermore, an extensive sensitivity analysis reveals that (1) switchgrass particles with rougher edges (due to different processing techniques) exhibit a higher shear strength and a lower flowability; (2) stiffer particles yield a lower bulk density (up to 21% lower) compared to more deformable particles, indicating particle deformability should be incorporated when modeling biomass flow in a preprocessing system.

To improve the thermal properties and maximum pressure of plastic pipes, a self-developed rotational shear system (RSS) was prepared in this study to form the plastic pipes containing high oriented shish-kebab through imposing rotational shear field. When the rotational shear was performed at 8 rpm, the hoop tensile strength, thermal conductivity in in-plane and heat resistance of the pipes increased by 235.9%, 34.4% and 32.6%, respectively. With the annealed temperature close to 125 °C for 40 min on the pipes, thin-lamella could be melted to the amorphous phase that facilitated the random chains rearrange on thick-kebab. Results showed that the lateral size and thickness of kebab increased by 4.6% and 5.2%. The higher thermal conductivity in in-plane and Vicat softening temperature, increasing to 0.534 w/(mk) and 112.4 °C, were attributed to the larger region of interlocking shish-kebab throughout the pipe wall.

We present the asteroseismic study of the early red-giant star KIC 4448777, complementing and integrating a previous work (Di Mauro et al. 2016), aimed at characterizing the dynamics of its interior by analyzing the overall set of data collected by the {\it Kepler} satellite during the four years of its first nominal mission. We adopted the Bayesian inference code DIAMOND (Corsaro \& De Ridder 2014) for the peak bagging analysis and asteroseismic splitting inversion methods to derive the internal rotational profile of the star. The detection of new splittings of mixed modes, more concentrated in the very inner part of the helium core, allowed us to reconstruct the angular velocity profile deeper into the interior of the star and to disentangle the details better than in Paper I: the helium core rotates almost rigidly about 6 times faster than the convective envelope, while part of the hydrogen shell seems to rotate at a constant velocity about 1.15 times lower than the He core. In particular, we studied the internal shear layer between the fast-rotating radiative interior and the slow convective zone and we found that it lies partially inside the hydrogen shell above $r \simeq 0.05R$ and extends across the core-envelope boundary. Finally, we theoretically explored the possibility for the future to sound the convective envelope in the red-giant stars and we concluded that the inversion of a set of splittings with only low-harmonic degree $l\leq 3$, even supposing a very large number of modes, will not allow to resolve the rotational profile of this region in detail., accepted for publication on ApJ

Developed to aid in the design of hoppers and silos, the shear cell is now frequently used to rank the flowability of powders relative to one another. While standards, such as ASTM D6773 and D6128, exist for shear cell tests, there are still differences between commercially available shear cell testers, such as cell geometry and size. In this work, we used two materials, a free-flowing alumina and a cohesive alumina, to compare measurements from three commercially available rotational shear cells. Results were collected and compared for cohesion, unconfined yield stress, major principal stress, pre-shear stress, flow function coefficient, bulk density, effective angle of internal friction, and the angle of internal friction. ANOVA methods were used to determine the statistical significance and relative size of each of these effects. This work has found that while, as expected, the material type has the largest effect on the shear cell results, the consolidation at which the material was tested and the tester type are also statistically significant effects. These results indicate that care should be taken when comparing the results between different shear cells.

The design of a novel apparatus, the Glen Withy torque tester (GWTT), for measuring horizontal shear properties in equine sport surfaces is described. Previous research has considered the effect of vertical loading on equine performance and injury but only limited discussion has concerned the grip or horizontal motion of the hoof. The horizontal support of the hoof by the surface must be sufficient to avoid excess slip without overloading the limb. The GWTT measures the torque necessary to twist an artificial hoof that is being pushed into the surface under a consistently applied vertical load. Its output was validated using a steel surface, then was used to test two sand and fibre surfaces (waxed and non-waxed) through rotations of 40–140°, and vertical loads of 157–1138 N. An Orono biomechanical surface tester (OBST) measured longitudinal shear and vertical force, whilst a traction tester measured rotational shear after being dropped onto the surfaces. A weak, but significant, linear relationship was found between rotational shear measured using the GWTT and longitudinal shear quantified using the OBST. However, only the GWTT was able to detect significant differences in shear resistance between the surfaces. Future work should continue to investigate the strain rate and non-linear load response of surfaces used in equestrian sports. Measurements should be closely tied to horse biomechanics and should include information on the maintenance condition and surface composition. Both the GWTT and the OBST are necessary to adequately characterise all the important functional properties of equine sport surfaces.

Background Court shoe designs predominantly focus on reducing excessive vertical ground reaction force, but shear force cushioning has received little attention in the basketball population. We aimed to examine the effect of a novel shoe-cushioning design on both resultant horizontal ground reaction forces and comfort perception during two basketball-specific cutting movements. Methods Fifteen university team basketball players performed lateral shuffling and 45-degree sidestep cutting at maximum effort in basketball shoes with and without the shear-cushioning system (SCS). Paired t-tests were used to examine the differences in kinetics and comfort perception between two shoes. Results SCS shoe allowed for larger rotational material deformation compared with control shoes, but no significant shoe differences were found in braking phase kinetics during both cutting movements (P = 0.35). Interestingly, a greater horizontal propulsion impulse was found with the SCS during 45-degree cutting (P P = 0.012). During lateral shuffling, there were no significant differences in horizontal GRF and comfort perception between shoe conditions (P > 0.05). Discussion The application of a rotational shear-cushioning structure allowed for better forefoot comfort and enhanced propulsion performance in cutting, but did not influence the shear impact. Understanding horizontal ground reaction force information may be useful in designing footwear to prevent shear-related injuries in sport populations.

The purpose of this study was to demonstrate that the flow function (FFc) of pharmaceutical powders, as measured by rotational shear cell, is predominantly governed by cohesion but not friction coefficients. Driven by an earlier report showing an inverse correlation between FFc and the cohesion divided by the corresponding pre-consolidation stress (Wang et al. 2016. Powder Tech . 294:105-112), we performed analysis on a large data set containing 1130 measurements from a ring shear tester and identified a near-perfect inverse correlation between the FFc and cohesion. Conversely, no correlation was found between FFc and friction angles. We also conducted theoretical analysis and estimated such correlations based on Mohr–Coulomb failure model. We discovered that the correlation between FFc and cohesion can sustain as long as the angle of internal friction at incipient flow is not significantly larger than the angle of internal friction at steady-state flow, a condition covering almost all pharmaceutical powders. The outcome of this study bears significance in pharmaceutical development. Because the cohesion value is strongly influenced by the interparticle cohesive forces, this study effectively shows that it is more efficient to improve the pharmaceutical powder flow by lowering the interparticle cohesive forces than by lowering the interparticle frictions.

The measurements performed in Chaps. 3 and 4 can be used to make more quantitative statements about the internal rotation profile of the studied stars. We determined that the difference in the rotational splittings as a function of frequency is not large, consistent with what would be observed in the Sun if viewed as a star. In addition to this we found that the spot rotation periods are consistent with the seismic rotation periods; showing that any radial or latitudinal differential rotation is likely small. In this section we will use forward modeling with a simple radial step rotation profile and investigate how well the above mentioned measurements can constrain such a model. This will allow us to estimate the upper limits of the radial shear at the tachocline.

SUMMARY This study focuses on non-coaxial flow behavior of cohesionless soil undergoing cyclic rotational shear, with a special interest in the effects of particle-scale characteristics. To this end, we perform a series of 2D discrete element simulations with various particle shapes, inter-particle coefficient of friction, initial density, and stress ratios. The validity and efficacy of the numerical model is established by systematically comparing numerical simulation results with existing laboratory testing results. Such comparison shows that the numerical simulations are capable of capturing mechanical behavior observed in laboratory testing under rotational shear. We further demonstrate and quantify a strong yet simple relationship between the deviatoric part of the normalized strain increment and the non-coaxial angle, denoted by ΔeqR and ψ, respectively. This quantitative correlation between ψ and ΔeqR is independent of applied stress ratio, initial and current void ratio, and the number of cycles applied, but dependent on the principal stress orientation and particle-scale characteristics. At the same ΔeqR, specimens with higher inter-particle friction angle or smaller particle aspect ratio show greater non-coaxial angles. A simple model ψ=45∘mΔeqR is able to fit this ψ-ΔeqR relationship well, which provides a useful relationship that can be exploited in developing constitutive models for rotational shearing. Copyright © 2014 John Wiley & Sons, Ltd.

This paper presents a magnetorheological (MR) brake design by using additional squeeze working mode to an existing conventional rotational shear. The MR brake was designed with consideration given to a new concept of braking mechanism with the help of magnetic simulation. Important parameters such as disc brake dimensions, clearance gap and electromagnetic coil configuration were taken into account when constructed the MR brake. Simulation results showed that the magnetic field strength was at best by having the magnetic coil beside the non-magnetic material, which was located at the end of the outer diameter. Meanwhile, the value of magnetic field was greater than when a small squeeze gap was applied. Eventually, the design will provide an opportunity to study and consequently understand on how the MR fluids react to such operating condition in order to be realized in the MR brake.

Highly concentrated suspensions have complex structures that complicate their characterization and study. Highly concentrated suspensions of Ag particles in ethyl cellulose solutions (Ag pastes) were thus studied and dual rheological responses were observed. Under rotational shear, the unpredicted enhancement of shear moduli occurred in the low frequency regime, showing that rheological responses of Ag pastes were strongly influenced by fillers. Under large-amplitude oscillation, the hydrodynamic-induced enhancement effect was observed over the whole frequency range, showing that rheological responses of Ag pastes were dominated by the binder solutions. Further studies showed that this dual behavior arose from the dual nature of structures in Ag pastes. The different shear types promoted the development of different structures in rheological experiments. Rotational shear promoted cluster formation, resulting in the unpredicted enhancement; while large-amplitude oscillation broke the clustering, leading to the hydrodynamic enhancement. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Suspensions of bleached bagasse pulp at 0% to 15% mass concentrations were sheared in a concentric cylinder rotary device to study the pulp suspension’s fluidization properties. The use of a baffled chamber, with blade rotors, imposed shear stress within the suspensions and prevented slip at the chamber walls. Linear-type, hollow-type, and screw-type rotors were used to explore the influence of rotor structure on fluidization properties. The torque was measured as a function of rotational speed. The torque vs. rotational speed curves and flow phenomenon were found to depend on the mass consistency of the pulp suspensions and the gap between the rotor and chamber. The structure of the rotor had little influence on the fluidization of the pulp suspensions, and the critical rotational speed that makes the pulp suspensions turbulent was similar for all rotor types. The gap between the rotor and chamber should be small to let pulp suspensions fluidize at low rotational speed.

Cementitiously stabilized layers (CSL) have been used extensively by highway agencies over the years. The erosion of CSL can cause several distresses in flexible and rigid pavements. The three necessary conditions for the occurrence of erosion are heavy loads, sufficient moisture, and the presence of erodible materials. The Mechanistic-Empirical Pavement Design Guide (MEPDG) provides a methodology for the analysis and performance prediction of pavements that incorporate CSL. However, test methods and models that specifically address the erosion of CSL have not yet been incorporated into the MEPDG. This study evaluates the existing test methods for erosion, including wheel tracking, manual wet-dry brushing, rotational shear device (RSD), jetting, a vibration table, or cyclic impact erosion (CIE), or combinations thereof. It is found that a CIE test is a robust test procedure that is used to quantify the erodibility of CSL. Based on the laboratory results from a CIE test, an empirical model that combines top-down compressive fatigue and erosion is developed to predict the erodibility of CSL. It is found that the developed model is effective in predicting both the top-down compressive fatigue and erosion of CSL. This test method and prediction model are recommended for incorporation into the MEPDG.

Many experimental studies have pointed out that failures or remarkable losses of strength may occur in sand–structure interfaces when they are subjected to cyclic rotational shear. This work introduces an interface model based on the Generalized plasticity theory to describe the effects of cyclic rotational shear on the mechanical behavior of sand–structure interfaces. The simulative capabilities of the model are then presented for various stiffness boundary conditions.